Devices that fire frangible projectiles are known in the art. For example, marking guns (commonly known as paintball guns) typically use compressed gas to propel frangible projectiles. The frangible projectiles commonly have a gelatinous or plastic shell designed to break upon impact. Typically, the shells are filled with a marking material, such as paint, and/or an immobilizing material, such as a noxious chemical.
These types of devices have a wide variety of applications. For example, a popular recreational use is in paintball games, in which opposing sides attempt to seek out and “shoot” one another with paintballs. Frangible projectiles have also been used to segregate cattle within a herd. Likewise, law enforcement personnel employ frangible projectiles with immobilizing materials for crowd control.
The fragile nature of the projectiles often creates difficulties in reliably firing the device. Typically, the firing mechanism includes a bolt that pushes a frangible projectile into a barrel of the device when the user pulls the trigger. In some cases, however, the projectiles may become partially inserted into the breech. When this happens, the bolt tends to shear or rupture the projectile, which fouls the breech and barrel of the weapon.
Electrical and mechanical systems have been proposed to solve this problem. For example, some devices employ optical sensors to sense the presence of a projectile in the breech of the marker. These systems seek to prevent accidental rupturing by preventing firing when the projectile is not wholly within the device's breech. If a rupture occurs in the breech, however, the optics of such systems can become fouled, typically rendering the system unreliable or possibly even inoperable. Spring-loaded bolts have also been proposed to prevent accidental rupturing of projectiles during firing. In these devices, the spring drives the bolt with less force than that required to rupture a projectile. However, the spring's weak force is typically insufficient to withstand pressure exerted on the bolt during firing. This tends to move the bolt rearward to a position where gas may flow into the projectile feed port, which interferes with loading of the weapon.
Therefore, there exists a need for a firing mechanism that operates in a reliable manner, while preventing the rupturing of projectiles during firing.